The objectives of this study are to characterize the structural and functional properties of a low-molecular-weight, high- affinity calcium-binding protein from squid optic lobes. This protein (SCaBP) coexists with calmodulin in significant amounts in the cytoplasam of the squid nervous system, a tissue source which has provided important model systems for many studies of nervous function. We have shown SCaBP to have a very similar sequence to calmodulin but to have a few, potentially important, differences. The differences in SCaBP structure enable it to have distinct functional properties from calmodulin, responding differently to the calcium signal. We aim to use equilibrium dialysis, UV spectroscopy and NMR techniques to characterize its structure. Functional properties of the protein will be studied using affinity chromatography, immunoblotting and immunolocalization procedures. We believe the combination of these techniques will provide us with insight into the mode of action of this particular calcium-binding protein and possibly other members of this class of intracellular regulatory protein. Because of its role as a second messenger, calcium, and the calcium-binding proteins which mediate its effects, are of great importance in the regulation of nervous function. By improving our understanding of the mechanisms by which calcium exerts its effects we will improve our understanding of the regulation of normal nervous function and hence of potential defects which might lead to nervous disorders.